Heat generation during the aging of wood-derived fast-pyrolysis bio-oils

Tom Sundqvist, Yrjö Solantausta, Anja Oasmaa, Lauri Kokko, Ville Paasikallio

Research output: Contribution to journalArticleScientificpeer-review

10 Citations (Scopus)

Abstract

The changes in chemical composition and physical properties that accompany bio-oil aging reactions have been studied earlier. However, one fundamental aspect of this transformation process has been ignored. In this article, we prove that aging of fast-pyrolysis bio-oils from woody biomass is an exothermic process with notable heat generation under adiabatic conditions. The heat generation characteristics of several fast-pyrolysis bio-oils were studied in a novel reaction calorimeter that was made in-house. When typical fast-pyrolysis bio-oils were stored at 50 °C for a period of 1 week, they exhibited overall adiabatic temperature increases ranging from 14 K to 28 K. The largest differences in heat generation were observed at the beginning of the aging period, which corresponds with the previously known reactivity characteristics of bio-oils. Increasing the storage temperature accelerated the aging reactions, which manifested as higher overall temperature increases-up to 55 K in 1 week-and higher specific thermal power density (STPD) values. The reactivity of the bio-oil at 70 °C could be partly passivated by employing a 1 week pretreatment at a more moderate temperature (40 °C). The addition of alcohol decreased heat generation from the bio-oil. The observed heat generation of bio-oils under varying aging conditions correlated with changes in their chemical composition and physical properties. This shows that previously developed bio-oil stability indicators can also be used to estimate the heat generation potential of a given bio-oil. In particular, a change in the concentration of carbonyl compounds exhibited a clearly linear correlation with heat generation. A decrease of one unit in the carbonyl content (mol/kg of bio-oil) would correspond to an adiabatic temperature increase of 20 °C.
Original languageEnglish
Pages (from-to)465-472
JournalEnergy & Fuels
Volume30
Issue number1
DOIs
Publication statusPublished - 2016
MoE publication typeA1 Journal article-refereed

Keywords

  • heat generation
  • pyrolysis bio-oil
  • ageing

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